Known methods of identifying anisotropy of an image have certain disadvantages. Among these are those that from the projection, by means of a Radon transform, of the pixels of the image in two projection directions that are parallel to the edges of the image. One limitation of this method is that only an anisotropy of the texture oriented in one of these directions can be identified. If the image has an anisotropy oriented in some other direction, for example the direction of a diagonal of the image), then it will not be correctly identified.
Although it is possible to project the image in additional directions to alleviate this problem, this is not desirable. In practice, the digital image is defined as a set of pixels placed on a discrete grid or matrix (“lattice”), that is to say that the pixels have for positions points in the space d. It is not desirable to define projections in other directions of the image because the projected points would no longer belong to the lattice. This makes it necessary to interpolate, from the projected points, the values of the pixels that belong to the lattice. This introduces an error and degrades the reliability of the method.
There is therefore a requirement for a method for identifying, with satisfactory reliability, the anisotropy of the texture of an image in any direction.